1. Field of the Invention
The invention relates generally to glassware forming machines of the rotating table type having a plurality of continuously rotating, circumferentially spaced forming units. More particularly, the invention relates to a timing control system for controlling the delivery of gobs of molten glass to the continuously rotating blank molds of the machine.
2. Description of the Prior Art
Glassware forming machines of the rotating table type are well known in the glassware manufacturing industry. One type of such machine is shown in U.S. Pat. No. 1,979,211 and is commonly referred to as the "Emhart H-28 Machine." This type of machine is a single table, continuous rotary motion machine having a plurality of individual sections or forming units mounted for rotation about the axis of the machine. These machines have been available with different numbers of individual forming units, thus constituting, for example, a 6, 12 or 18 section machine. In such H-28 machines each individual forming unit produces one glassware article for each complete revolution or cycle of the machine and will therefore be referred to herein as H-28 single gob machines.
A significant improvement over the H-28 single gob machine is disclosed in U.S. Pat. No. 4,339,264 which describes an H-28 double gob machine where each individual forming unit produces two glassware articles for each complete cycle. This patent is hereby incorporated by reference in this disclosure in its entirety.
One of the unique features of the prior art H-28 double gob machine is its delivery system, that is, the manner in which it guides or delivers gobs to the continuously rotating blank molds of the machine. Each set of inner and outer blank molds has associated with it a gob guiding unit consisting of a scoop, trough and deflector for guiding gobs into the blank molds. Each gob guiding unit oscillates over predetermined arcuate path about a delivery system axis parallel to the machine axis so that in one arcuate direction the speed of the deflector of the gob guiding unit approximates that of the continuously moving blank mold to facilitate gob delivery.
The delivery of gobs to the blank molds of a continuously rotating H-28 machine, whether single or double gob, is quite important. The gob must be delivered by the gob guiding unit while the blank molds are moving. In the H-28 single gob machine this may be accomplished by matching the arcuate speed of the gob guiding unit (in at least the direction where it moves with the blank) to that of the continuously moving blank mold. The same problem exists in H-28 double gob machines although compounded by the fact that, in addition to both gobs having to be delivered while the corresponding molds are moving, both gobs should be delivered at the same time with respect to each other.
In prior art H-28 double gob machines it was found that various factors influence the gob drop time (i.e. the time required for a gob to drop from the shears to its associated blank mold) so that even though two gobs may have been cut simultaneously they may not enter their corresponding blank molds simultaneously. This may result in defective ware being produced in one or both molds. This situation is somewhat exacerbated when arcuate shears are used since the gobs may then not even be cut simultaneously. Accordingly, it is an object of this invention to provide a means for determining the gob drop time of each gob within a group of gobs being delivered and for adjusting one or both of the gob drop times of subsequent gobs in order to equalize both drop times. It is also an object of this invention to provide means for synchronizing gob delivery and gob reject to the machine cycle.